Per-session MCP tool surface (JSON-RPC 2.0)

JSON-RPC 2.0 over HTTP POST. Exposes workflow tools, A2A peer agents as tools, and agent memory tools to running agent subprocesses. Supported methods: - `initialize` - protocol handshake, advertises `tools` capability. - `notifications/initialized` - client readiness signal; no response (202). - `tools/list` - lists tools available for this session. - `tools/call` - invokes a tool by name with arguments. Server-injected context: memory tools (`af_memory_recall`, `af_memory_remember`) and graph tools (`graph_*`) have their `context` argument overwritten from the authenticated session to prevent cross-tenant access. Auth: `Bearer rsk_*` via `getCliOrSessionAuth`. The authenticated org must match the session's `organizationId`. JSON-RPC error codes: - `-32700` Parse error - `-32601` Method not found / ToolNotFoundError - `-32602` Invalid params - `-32603` Internal error - `-32003` Rensei auth-denied (ToolNotAuthorizedForSessionError)

curl -X POST "https://example.com/api/mcp/string" \  -H "Content-Type: application/json" \  -d '{    "jsonrpc": "2.0",    "method": "initialize"  }'

{
  "jsonrpc": "2.0",
  "id": "string",
  "result": null,
  "error": {
    "code": 0,
    "message": "string",
    "data": null
  }
}

{
  "error": "Session not found"
}

{
  "error": "Session not found"
}

{
  "error": "Session not found"
}

{
  "error": "Session not found"
}